Method of treating synthetic proteinaceous fibers



Patented Sept. 24, 1946 METHOD or 'rnm'rmo srn'rnarro mornmecaocs mans Francis Clarke Atwood, Newton, Mass assignor to National Dairy Products Corporation, New

York, N. Y., a corporation of Delaware No Drawing. Application December 11, 1943,

Serial No. 513,952

This invention relates to the treatment of synthetically shaped protein-containin materials.

sirable properties that render them valuable for use in fabrics of all kinds, such as covering materials and upholstery, and for use in articles of clothing including clothes, shoes and gloves. These properties include the warmth, softness, flexibility, tensile strength, elasticity and other similar properties of protein-containing materials, and are hereinafter referred to as physical properties.

All proteins contain carbon, hydrogen, oxygen, and nitrogen and many proteins also contain sulfur and phosphorus. The proteins are thought to contain amino and probably hydroxy and carboxyl groups, and are more or less chemically reactive depending upon their individual constitution. For example, difierent proteins are affected difierently by hot'water, alkalin or soap solutions. Over long periods of time some proteins also oxidize or otherwise deteriorate more rapidly than others so as to become somewhat brittle and lose their strength and softness. Different proteins also react difierently with various other compounds, particularly dyes. In re- Ierring to the chemical properties of protein containing materials, reference is made to their ability to combine physically or react chemically with any other compound such as oxygen, water, acids, alkalies, and dyes.

While the physical properties of fiber prepared from the proteins such as casein, including the common method of soaking the shaped casein fiber in formaldehyde solutions are satisfactory for some purposes, they are far from satisfactory for most uses to which fibers are to be put. With respect to their chemical properties particularly they leave much to be desired. For example, a fiber prepared from a casein dispersion and coagulated, in which process it is hardened by the usual treatment with formaldehyde, is not carbon, in which acetic anhydride and a small 7 resistant to hot water or dilute acids or alkalies. Particularly is this so if the water solution ,contains an alkaline material such as would be present in' a hot solution of an ordinarysoap. Upon the heating or boiling of such fiber in such a solution it becomes soft and spongy and takes on a slimy feel. .The tensile strength of the fiber and its elasticity in such a state is also greatly reduced so that the fiber is readily deformed or broken. Upon drying such fiber after it has been subjected to such treatment, it becomes brittle so that further handling results in excessive droppings, if in fact the fiber is sufiiciently'flexible to be subjected to any further processing. Ordinary casein fiber, in addition, does not have dyeing properties enabling itto be dyed in a manner similar to naturally occurring proteinaceous fiber. The ordinary casein fiber also is subject to a change in properties due to contact with moisture in the air. In humid air it is relatively plastic, but in dry air it is quite brittle.

From the above it wil1 be seen that the synthetic protein fiber as known heretofore in the art, such as that shaped from casein and hardened with formaldehyde, is entirely different from natural proteinaceous fiber such as wool,

' silk or fur, and is not suited for the uses to which such natural fibers may be put. This difference is so marked as.not to be simply a matter of degree. Apparently the casein inherently is of such a nature as not to possess satisfactory properties for fiber purposes. Attempts at modifications of the casein have not produced a fiber which has satisfied the textile industries.

In copending application, Serial Number 427,940, filed January 23, 1942, of which this application is a continuation-in-part, a process is described in which the chemical properties of synthetic protein materials may be changed by reaction with certain chemical compounds to impart more desirable chemical properties without detracting from their Physical properties. They may be made more resistant to chemical activity but at the same time remain soft and pliable and retain or even improve their tensile strength and other physical properties.

In accordance with the Process-described in the aforesaid co -pending application, the synthetic proteinaceous fiber is treated in a liquid containing an acylating anhydride, more particularly, acetic anhydride in an inert solvent. .The treating liquid comprises an inert organic solvent, such as a hydrocarbon or a chlorinated hydroamount of acetic acid is included. The proteina- 3 ceous fiber to be treated is made by dispersing casein or other proteinaceous material in an alkaline solvent and spinning it into an acidic coagulating bath, following which it is treated with formaldehyde, washed and dried. The dried fiber so prepared is immersed in the treating liquid at an elevated temperature of about 150 to 225 F. for a period of a few minutes to an hour, following which the fiber is removed from the liquid.

q The 'proteinaceous fiber to be treated normally contains a small amount of water which is the normal moisture content of the fiber when'it is in equilibrium with an atmosphere of ordinary temperatures and humidities. This is reduced as much as possible, in accordance with the process in said co-pending application, since the moisture in the fiber reacted with .the acetic anhydride in the treating liquid to form acetic acid. This used up aceticanhydride for no good purpose, and was thought to increase the acetic acid content to a point where it must be eliminated. In fact, in accordance with the process of saidapplication, a portion of the treating liquid is withdrawn and neutralized with soda ash-to con- ,vert the acetic acid to sodium acetate which is separated from the treating liquid.

It has been discovered, in accordance with the invention described in this application, that if the amount of acetic acid in the treating liquid is increased, a vastly superior fiber is obtained, and furthermore, that by treating the fiber in the liquid containing the increased amount of acetic acid, it is unnecessary to neutralize the acid in the treating liquid, since the fiber asit is removed from the treating liquid will carry with it an amount of acetic acid absorbed therein which is equivalent to that formed by the reaction of the water in the fiber to be treated with acetic anhydride. Inother words, it has been discovered that the moisture content of the fiber I can be adjusted as to produce an amount of acetic acid during the treating process which will be absorbed in the fiber during the treatment if the amount of acid carried in the treating liquid is at a sufllciently high level. Not only is the neutralizing eliminated in this way, but a, superior acetylation of the fiber results, apparently due .to the larger amount of acid in association with the acetic, anhydride in the treating solution.

In accordance with the invention a fiber may be "produced that has a superior resistance to chemical activity of the undesired type, such as breakdown by bleaching agents and deterioration by hot water, acids, or alkalides, while at the same time it has superior chemical properties imparted to it with respect to its reaction to dyestufis and chemicals ordinarily used in the process of naturally occurring proteinaceous fibers. The fiber also remains unusually soft and pliable and retains or even has its physical properties improved. It acquires to a greater extent those properties desired by textile operators.

The fiber produced can better withstand boiling for long periods of time in water, as well as in hot dilute acid solutions such as are used in dyeing. It is also enabled better to withstand vigorous mechanical treatment combined with alkaline material, such as fulling" and scour- I accepted by natural protein fiber. Since one of the more important-uses of the synthetic protein fiber is in admixture with natural protein fiber and other fibers natural or synthetic, "it is desirable that the two should have similar dyeing propknown in the trade as Solvasol," is inexpensive and for that reason is preferred. To this is added acetic anhydride in an amount of 7 to 8%, and acetic acid in an amount of 5 to 7%, preferably 5 /2 to 6% by weight of the total treating liquid. The amount of the acetic anhydride in the above formula may vary from 5% to 15%. Amounts less than 5% will result in some acetylation but generally it is not sufficient to Justify the treating of the fiber by the process; an amount above 10% (unless lower temperatures are used) does not result in a sufllcient improvement to warrant using a larger amount, but no harm is done by its presence. The temperature may vary from about 150 F. to 225 F. At lower temperatures the reaction is slower, and therefore, on a comnrercial scale there is no advantage in using the lower temperatures. The temperature should not be so high as to cause yellowing or softening of the fiber during treating. The maximum temperature will depend somewhat on the protein from which the fiber is made and the presence in the fiber of ingredients which tend to yellow or char at lower temperatures. It is possible in all instances to operate at atemperature below the harmful temperature and at which the reaction rate permits the treatment to be concluded percentage is critical if the fiber is to have the desired dyeing properties. While the acetic acid, as such, apparentlyv is not an acetylating agent, and the acetylating reaction is apparently attributed to the acetic anhydride, nevertheless the presence of a critical amount of acetic acid has a great effect on the nature and extent of the acetylatlon and the properties of the fiber. If

too little is present, the resulting filber has unde- 'sirable dyeing properties and absorbs dyestufis' I which ordinarily do not dye wool. On the other hand, id the acid concentration is too great, the fiber becomes too soft and is poorly acetylated. By controlling the amount of acetic acid between the above critical limits it is possible to produce a fiber which has dyeing properties closely simu-' lating that of natural wool and which resists dyes which do not dye wool and is dyed'by dyes which ordinarily dye wool and at about the same rate.

The selection of these variables In carrying out the process, a treating liquidis prepared in accordance mula, and about 300 gallons is used for each 275 pounds of the fiber to be treated. The'fiber is placed in the liquid and agitated therein while the liquid is maintained at a temperature of 150 the fiber may be placed under a vacuum and as much of the treating liquid vaporized as possible.

with the above for- The proteinaceous fiber at the time it is introduced into the treating solution preferably should have a moisture content of between 3 to 6%. The moisture in the fiber reacts with a portion of the acetic anhydride to form acetic acid. However, it is a characteristic of the fiber that it absorbs acetic acid, and the amount of acid formed by this reaction is absorbed in the fiber when the acetic acid concentration is maintained within the above defined critical limits. When the fiber 'is removed after the conclusion of the process, it carries with it acetic acid equivalent to that formed by the reaction of the water with the acetic anhydride. Before the next batch of fiber is treated in the treating liquid, additional acetic anhydrlde is added to bring the concentration up to the desired amount. Thus for each batch of fiber it is necessary only to add acetic anhydride equal to that which combines with the protein and is converted to acid by reaction with the water in the fiber, together with an amount of solvent equivalent to that absorbed by the fiber or lost evaporation.

When the moisture content is reduced to within the above range, the process is adapted for continuous re-use of the treating liquid as explained above. This does not mean that fiber with a higher or lower moisture content cannot be used. Since it is very difiicult to dry the fiber to a moisture content of less than 3% without harming it, there will be few, if any, occasions to practice the process with a fiber of a lower moisture content. It is possible to treat a fiber with a higher moisture content but the amount of acetic acid formed by reaction of this amount of moisture with acetic anhydride is in excess of that which is absorbed by the fiber and removed with it when the acid concentration is within the above critical limits. Under the circumstances it is necessary to start with a treating liquid. having an amount of acid, so that the acid produced in the treatment, which is in excess of that absorbed by the fiber, brings the acid concentration of the treating liquid within the critical range. If the treating liquid is to [be re-used for treating more fiber of higher moisture content, it is necessary to neutralize the excess acid.

After the fiber is removed from the treating solution, it is washed thoroughly with water and the acetic acid absorbed in the fiber is washed out, leaving the fiber relatively free from acid. It is unnecessary to use neutralizing or other basic ingredients in the wash water, although the into an acidic coagulating bath which may contain a tanning agent. A process, which may be used is described in co-pending application Serial Number 309,028, filed August 23, 1939, (which to the fiber and the ingredients contained in the matured as Patent No. 2,342,994 on February 29, 1945) but other processes may be employed in making the fiber, and the process is not critical.

The fiber should be treated with formaldehyde after thespinning and before the treatment in accordance with theinvention. Preferably the fiber after spim'ling is soaked in one or more formaldehyde containing baths and then washed and dried. Alternatively it may be treated with formaldehyde vapor. A process of treating spun fiber with formaldehyde is described in copending application Serial Number 417,024, filed October 29, 1941, but other processes may be used.

The protein may be any alkaline-dispersible acid-coagulable protein. The protein from milk,

termed animal casein, and the protein from soybeans, often referred to as vegetable casein, may be used advantageously and these materials are included in the generic designation of casein as used herein. Other proteins, such as those obtainled from peanuts, seeds, hair, etc., may be use The process of the invention is simple to "opcrate, and may be practiced in a continuous semicontinuous or batch operation. It requires a minimum' of materials, and temperatures that are readily obtainable. It has the advantage of simplicity of operation as well as the production of a superior fiber.

An important advantage of the invention resulting from the control of the acetic acid content within the above critical limits during the acetylation is the rate of dye absorption. Not only may the fiber produced in accordanc with the invention absorb dyes which act on ,wool and resist non-wool dyes, but the fiber may absorb the dye at about the same rate as does wool in suitably controlled dye baths. This is an import-ant property, since it is important that a uniform product be produced insofar as dyeing properties are concerned. In the dyeing of mixed goods it is also important that the different fibers of the mixture should all be the same shade as the result of treatment for a given length of time in the dye bath. If one of the fibers, for example a synthetic proteinaceous fiber, absorbs the dye at a faster or slower rate than another fiber, the dyed synthetic fiber will be darker or lighter, respectively, than the natural wool dyed therewith. It is entirely unobvious that the concentration of acetic acid, which is not an acetylating agent itself, rather than the concentration of acetic anhydride, should afiect and control the dyeing properties of the fibers.

The process is subject to the variation in materials and conditions described herein, and all of the same are included in the invention as are within the following claims.

I claim:

1. A process of treating a synthetically formed protein-base fiber produced by shaping into fiber form an alkali-soluble acid-coagulable protein comprising casein and treating it with formaldehyde, which process comprises treating said fiber while having a moisture content of about 3 to 6% in a treating liquid at a temperature within the range of to 225 F., said treating liquid comprising an organic solvent inert with reference liquid and containing about 5 to 15% acetic anhydride and about 5 to 7% of acetic acid, the temperature and the amount of acetic anhydride within the above ranges being selected with reference to each other and to the fiber'being treated so as to impart more desirable chemical prop- 7 erties to the fiber without undue yellowing thereoi. and removing the fiber from the treating liquid having absorbed thereinl substantially the amount 0! acetic acid formed by reaction of the moisture in the fiber with the acetic anhydride in the treating liquid as a result of the specified moisture content 01' the fiber and the acid content of the bath. a

2. A process of protein base fiber produced by shaping into fiber form an alkaliluble acid-coagulable protein comprising casein and treating it with formaldehyde, which process comprises treating said fiber while having a moisture content of about 3 to 6% treating a synthetically formed tent of the bath.

225' r. for 10 minutes to 2 hours, said treating liquid comprising an organic solvent inert with reference to the fiber and the ingredients contained in the liquid and containing. about 5 to 15% acetic anhydride and about 5 to 7% of acetic acid, and removing the fiber from the treating liquid having absorbed therein substantially the amount or the acetic acid formed by reaction oi the moisture in the fibernwith the acetic anhydride in the treating liquid as a result or the specified moisture content of the fiber and the acid con- FRANCIS CLARKE A'I'WOOD. 

